Category Archives: The Liminal Times

5 Things Science Still Can’t Explain (And No, TikTok Isn’t One of Them)

1. How Acetaminophen Works

A bottle of Tylenol on a dark background.

You’d think that the accessibility of acetaminophen (Tylenol) as an over-the-counter painkiller would indicate a full understanding of its medicinal properties, but Big Pharma is still trying to figure this one out. Certainly scientists know the dangers of excessive doses, but exactly how the medication works to ease pain is still a mystery. It was once thought that acetaminophen functioned in the same manner as nonsteroidal anti-inflammatory drugs (NSAIDs) such as aspirin and ibuprofen, which block the formation of pain-producing compounds in the central nervous system. However, further testing indicated that this enzyme suppression only happens under certain chemical conditions in the body. Other researchers have examined the effects of acetaminophen on neurotransmission in the spinal cord, but a definitive mechanism remains elusive.

2. Why Cats Purr

A cat looks directly at the camera while laying on the floor.

This one’s easy – cats purr because they’re happy you’re petting them, right? Except they also purr when they’re hungry, nervous, or in pain, so there are more complex matters to consider. One theory put forth by bioacoustician Elizabeth von Muggenthaler suggests that purring functions as an “internal healing mechanism,” as its low-frequency vibrations correspond to those used to treat fractures, edema, and other wounds. Additionally, since humans generally respond favorably to these soothing sounds, it’s possible that purring has evolved, in part, as a way for domesticated kitties to interact with their owners. And researchers at least believe they now know how purring happens – a “neural oscillator” in the cat brain is thought to trigger the constriction and relaxing of muscles around the larynx – so it may not be long before they home in on more precise reasons for this common, but still mysterious, form of feline communication.

3. How Bicycles Remain Upright

A man walks his bicycle along a crosswalk on a city street.

It’s one of the great ironies of life that we supposedly never forget how to ride a bicycle yet lack a firm understanding of the mechanics that enable us to pull it off in the first place. Early attempts at rooting out answers gave rise to the “gyroscopic theory,” which credits the force created by spinning wheels with keeping bikes upright. This theory, however, was disproven in 1970 by chemist David Jones, who created a functional bike with a counter-rotating front wheel. Jones then floated his “caster theory,” which suggests that a bike’s steering axis, pointing ahead of where the front wheel meets the ground, produces a stabilizing “trail” similar to a shopping cart caster. However, this theory also has holes, as researchersdemonstrated in a 2011 Science article showing that a bike with a negative trail – a steering axis pointing behind the wheel – could maintain balance with proper weight distribution. All of which goes to show that while biking is largely a safe activity, there remains a glaring question mark at the heart of a $54 billion global industry.

4. How Animals Migrate

A flock of geese flying over a body of water while the sun sets.

Maybe you’ve seen flocks of birds flying overhead to mark the changing of seasons or read about salmon fighting upstream to return to their birthplaces, but exactly how do these animals navigate in the midst of long distances and shifting geological conditions? In some cases, there are strong olfactory senses in play; a salmon can detect a drop of water from its natal source in 250 gallons of seawater, helping to guide the way “home.” But the possibilities get even stranger, as scientists are exploring the concept that light-sensitive proteins in the retinas of birds and other animals create chemical reactions that allow them to “read” the Earth’s magnetic field. It may seem far-fetched to think that birds rely on principles of quantum mechanics, but there may be no better explanation for how, say, the Arctic Tern stays on target while annually migrating more than 40,000 miles from pole to pole.

5. Why We Sleep

An alarm clock sits on a nightstand while a woman sleeps in the background.

Given that we can pinpoint the health benefits and problems associated with proper and insufficient amounts of sleep, it’s baffling that we still don’t fully understand what this all-important restorative state does for the body. Older theories followed the notion that sleep helps people conserve energy while keeping them away from the dangers of the night, while more recent research explores how sleep contributes to the elimination of toxic neural buildups andpromotes plasticity, the brain’s ability to adjust and reorganize from its experiences. Other experts hope to come across answers by studying glia cells, which are abundant in the central nervous system and possibly involved with regulating when we nod off and awaken. And if these diligent researchers ever do crack the code of what sleep does for us, maybe it will shed light on related nighttime mysteries — like why we dream.

Night night.

As Opposed to The Human Brain

The human skull never stops growing.

By the time most of us reach age 20 or so, the bones in our body are pretty much done growing. The growth plates that cause us to put on inches in our youth are now hardened bone, and in fact, adults tend to drop an inch or two in height as worn-out cartilage causes our spines to shrink over time. However, there are a few bones that buck this biological trend. Skulls, for example, never fully stop growing, and the bones also shift as we age. A 2008 study from Duke Universitydetermined that as we grow older, the forehead moves forward, while cheek bones tend to move backward. As the skull tilts forward, overlying skin droops and sags.

The skull isn’t the only bone that has a positive correlation with age. Human hips also continue to widen as the decades pass, meaning those extra inches aren’t only due to a loss of youthful metabolism. In 2011, researchers from the University of North Carolina School of Medicine discovered that hips continue to grow well into our 70s, and found that an average 79-year-old’s pelvic width was 1 inch wider than an average 20-year-old’s. So while it’s mostly true that humans stop growing after the age of 20, nature always likes to throw in a few exceptions to the rule.

The Woke Sea

Oysters can change their gender multiple times in their lifespans.

Within 12 hours of their birth, oysters begin pulling calcium out of the water to create their signature shells. For the first few weeks of their lives, these newborn bivalves zoom around in a current until they eventually settle on some hard substrate, whether it’s a rock, pier, or another oyster. This place of protection is where the oysters will spend the rest of their lives (which can be as long as 20 years). Eventually, usually a year after birth, it’ll be time for the oysters to breed, and that’s where things get interesting. 

Although born male, oysters have the impressive ability to switch their sex, seemingly at will. Every season, females can release up to 100 million eggs, and the amount of sperm released is so high it’s essentially incalculable. Once the egg and sperm are released, the oysters rely on pure chance for fertilization to take place, as the egg and sperm meet in the open water. Because any resulting larvae are extremely vulnerable to predators (especially filter feeders), oysters have evolutionarily compensated by being one of the most virile and sexually flexible species in the world — meaning that their ability to change sex likely evolved as a matter of survival. This impressive fecundity means that natural oyster reefs can grow to tremendous size; as little as 10 square feet of reef can house up to 500 oysters. Scientists theorize that water temperature could play a role in triggering whatever causes an oyster to change its sex, but many aspects of the process remain a mystery.